This invention relates to an improvement of a press-in contact composed of a connection portion to be connected to an electric cable, a circuit of a board or the like, a contact portion to contact a contact of a mating connector, and a press-fitting portion adapted to be fitted in a through-hole of a printed circuit board by press-fitting in a manner eliminating any damage to the press-in contact and the plated through-hole of the printed circuit board, which would otherwise occur.
Hitherto used press-in contacts of this kind are generally made of phosphor bronze or beryllium copper. It is ideal to construct a press-in contact so as to uniformly distribute the stresses on the inner wall of a cylindrical through-hole of a printed circuit board when the press-in contact has been fitted in the through-hole by press-fitting. For this purpose, the press-in contact disclosed in Japanese Patent Application Opened No. H7-245131 includes the press-fit pin having a press-fitting portion which is elastically deformable in its cross-section and adapted to be fitted in a through-hole of a printed circuit board by press-fitting. This press-fitting portion is characterized to have a V-shaped cross-section.
Moreover, Japanese Patent Application No. 186,273/94 filed on Jul. 15, 1994, with Opened No. H8-31476 corresponding to U.S. Pat. No. 5,667,412 filed by the assignee of this application discloses the press-in contact having a press-fitting portion whose inner periphery forms a U-shape groove and outer periphery consists of two arc portions and a straight portion. The straight portion is located between the two arc portions. Circles inscribing the inner periphery and circumscribing the outer periphery are in an eccentric relation and the thickness of walls of the two arc portions becomes progressively thinner toward the open end of the U-shaped groove to provide longer outer peripheries contacting a through-hole.
With the former press-in contact of the prior art, on fitting it in a through-hole of a printed circuit board, the ends of the V- or U-shaped press-fitting portion at its open end have a springiness so as to be resiliently deformed easily, particularly, stepwise deformed at respective parts in accordance with irregularity in diameter of through holes. With the latter press-in contact of the prior art, as the parts of the contact to be press-fitted in a printed circuit board are circular arcs, the area contacting a through-hole becomes larger so that the printed circuit board is uniformly deformed.
With these known press-in contacts, however, due to the irregularities in diameter of through-holes and press-fitting stresses in excess of predetermined values, the distal ends of walls forming the U-shaped cross-section at its open end often tend to deform inwardly toward each other beyond the elastic limit and set in the excess deformation. As a result, the distal ends would separate from the inner wall of the through-hole to reduce the contacting area, resulting in unstable contact between the press-in contact and the printed circuit board and reduction in holding force therebetween.